The present invention relates to an electrolytic process and apparatus for decomposing water and in particular for the recovery of hydrogen and/or oxygen gases therefrom.
Hydrogen and oxygen gases do not exist in nature in relatively pure form and it is, therefore, necessary to devise ways for obtaining these gases from the natural compositions of which they are a constituent. While many different methods for recovering hydrogen and oxygen have been devised, the most frequently used method involves the decomposition of water by electrolysis, since water is relatively abundant and inexpensive, and electricity is generally readily available, although somewhat more expensive. The basic electrolytic process for the separation of hydrogen and oxygen gases comprises the passing of a direct electric current between an anode and a cathode arranged in dilute aqueous solution of an alkali (e.g., sodium chloride) thus decomposing the water into its basic constituents.
The generally accepted theoretical voltage for this type of electrolysis is 1.23 volts at room temperature. However, because of the overloading of hydrogen on the electrodes and the internal cell resistance itself, voltages of 2.0 to 2.5 or greater are generally required. A 15 percent sodium chloride soluticn using iron cathodes and nickel plated iron anodes with an asbestos diaphragm separating the electrode compartments operates at termperatures from 60 to 70 degrees centrigrade producing low yields of hydrogen, relative to the cost of electricity and incidental plant processing costs. Attempts at making the system more efficient by nickel plating the anode or by using more exotic noble metals have been tried. However, most of the known cells produce about 7.0 cubic feett of hydrogen and half as much oxygen per kilowatt hour. While the gases produced are 99.7 percent pure and are even suitable for hydrogenation of edible oils, the return of only 7 cubic feet per kilowatt hour still remains quite costly.
Incidentally, it has been recently proposed to employ hydrogen gas in the operation of internal combustion engines. As a consequence, new attempts have been made in improving electrolytic cells, so as to reduce not only costs, but to improve the hydrogen yield. To this end, reference may be made to U.S. Pat. Nos. 4,608,137, 4,528,947; 4,384,941; and 3,648,668. Notwithstanding the many attempts to improve electrolytic cell construction and the method for decomposing water and even the use of exotic materials, the efficiency of such cells have not been greatly improved over the basic parameters known for some time.
It is an object of the present invention to provide an improved process for the decomposition of water into hydrogen and oxygen gases which has greater efficiency and employs less power than heretofore known.
It is another object of the present invention to provide a continuous process for producing hydrogen and oxygen gas in an electrolytic cell which overcomes the disadvantages and inherent difficulties of the known devices. It is yet another object of the present invention to provide a electrolytic cell which is simple, non-corrosive and durable.
These objects together with other objects and advantages will be apparent from the following description.